Standard-sized door handle locksets are used to latch and secure hinged doors to a doorjamb-mounted strikeplate. These locksets typically require the drilling of a large, through-going hole in the face of the door and a perpendicularly extending, smaller hole in the edge of the door. Additional holes must be drilled in the edge of the door to retain the latchplate. The lockset and door handles are mounted to both sides of the larger hole, and the latchplate and cylinder latch are mounted to the smaller hole on the edge of the door.
Typically, the center of the larger hole, which is located in the face of the door, must be either 2⅜ or 2¾ inches from the edge of the door, depending on the type or brand of lockset to be installed. To facilitate the drilling of the holes in the door, most of such locksets include a paper template that the installer may affix to the door to mark the drilling holes for the lockset.
These paper templates have significant shortcomings, however. First, the non-durable templates must be taped to the door, and this may become a tedious task for carpenters who are charged with installing many locksets at a jobsite. Furthermore, because of the stretching of the template or the possibility of misaligning it on the door with the wrong marking line, it is very possible that one or more of the holes may be marked in the wrong location. The fact that interior doors typically are configured in at least two popular thicknesses (1⅜ inches and 1¾ inches) adds to the difficulty in accurately positioning the template. In addition to these problems with the template, it is often difficult to drill holes in the door edge and face that are perfectly aligned with their central axes perpendicular to each other. Such misalignment or misplacement may result in a poorly fitting lockset or a lockset that fails to properly engage the strikeplate on the door jamb. At worst, an entire door can be ruined and may need to be completely discarded if the holes are drilled improperly.
A particularly inexperienced user may even use the wrong size holesaw or paddle bit when using either of these template methods, thereby resulting in a large hole of an incorrect size. If the hole is too small for the lockset yet too large for the pilot drill of a holesaw, it may be impossible for the proper-sized holesaw to enlarge the hole accurately on center of the previous hole. A similar problem will arise when enlarging a preexisting lockset hole in a previously drilled door, in that it is extremely difficult to center the larger holesaw over the center of a preexisting hole. Because newer locksets typically require a 2⅛-inch hole in the face of the door instead of the previously popular 1⅞-inch hole, this has become an increasing problem.
In the past, some have attempted to solve some of the inaccuracy problems in lockset installation through the use of a more durable plastic template that allows the drilling of pilot holes in the door. Such a template is shown in U.S. Pat. No. 4,280,776. While the plastic template disclosed therein may have some advantages over a paper template, the tool is still prone to most of the inaccuracy problems discussed above. Furthermore, by only allowing the marking or drilling of pilot holes, additional time-consuming steps must be taken in preparing and drilling each door.